Channel Sounding - Speed and Multiple Devices

[MatthewP]

Hi,

We are evaluating BLE Channel Sounding for indoor localization of small mobile robots. We need 2D localization within the room, so we would need to measure the distance to multiple anchors.

We have some basic questions about this:

• How fast can a single distance measurement be performed? I've seen numbers in the range of 100ms?
• Is it possible to be paired with multiple anchors and perform BLE CS sequentially without having to establish a new connection each time?
• When can we expect an update of the SDK with CS support?

Thank you very much for your response.

BR, Matthew

[Simonr]

Hi Matthew

I got a reply from the devs now, and I'm still waiting on a specific answer on question 1, but here are some preliminary responses.

1. This is very situational, but it's worth noting that CS can be started by setting the max_procedure_count=0, that means that CS procedures will continue to run on the ACL indefinitely or until explicitly disabled. In principle you could start a new CS procedure every ACL interval (minimum 7.5ms). 7.5ms is most likely not getting enough CS measurements in that time to do any accurate distance estimatio., but you can configure it so that a new procedure starts once you have collected enough CS measurements in the current CS procedure, to continuously get new measurements.

2. Having multiple peripherals connected at the same time to do sequential CS should be possible in the current NCS 2.8.0 implementation, although we haven't done any testing on this. Note that the central device would be using a lot of memory to store CS measurements from each peripheral device it is connected to and performing CS with. The ACL interval also needs to be noticably higher for the conncetions in order to not get scheduling conflicts between different links.

Best regards,

Simon

[MatthewP]

Hi Simon,
thank you for your detailed response. Are there any news regarding question 1?

Also, w.r.t to your answer:
1. Since the calculation of the distance is done in the application layer, would it be possible to switch between each device for every ACL interval and aggregate the results on a per-device basis? For example, use 2 ACL intervals for device 1 and save its data, the next 2 ACL intervals for device 2, ... In the meantime, use the data from the steps for each device to calculate the distance more or less simultaneously.
2. Interesting note about scheduling conflicts. Even after reading quite a bit about ACL connection events, intervals, etc. I'm still not a 100% sure how it works. Shouldn't it be fine if I set the procedure count to 1 in the previous example and then go through the connected devices one-by-one?

Additional small question: am I correct in assuming that the nRF54L15 does not support the LE 2M 2BT PHY? I didn't find any mentions in the datasheet.

Thank you again for your great help and best regards,
Matthew